A redundant hydraulic system

Abstract

A hydraulic system comprising: a hydraulic fluid pressure source, a hydraulic fluid reservoir, a hydraulically driven actuator having a first chamber and a second chamber, and a valve assembly having a first pilot-operated directional control valve and a second pilot-operated directional control valve, each including: an inlet port fluidly connected for receiving high-pressure hydraulic fluid from the hydraulic fluid pressure source, an outlet port fluidly connected for draining hydraulic fluid to the hydraulic fluid reservoir, a first actuator port fluidly coupled with the first chamber of the hydraulically driven actuator, a second actuator port fluidly coupled with the second chamber of the hydraulically driven actuator; first to fourth fail-safe solenoid-controlled pilot valves; and a pilot pressure fluid supply system.

1 . A redundant hydraulic system comprising:
 a hydraulic fluid pressure source,   a hydraulic fluid reservoir,   a hydraulically driven actuator having a first chamber and a second chamber,   a redundant sectional or monoblock valve assembly having a first pilot-operated directional control valve and a second pilot-operated directional control valve, each including: an inlet port fluidly connected for receiving high-pressure hydraulic fluid from the hydraulic fluid pressure source, an outlet port fluidly connected for draining hydraulic fluid to the hydraulic fluid reservoir, a first actuator port fluidly coupled with the first chamber of the hydraulically driven actuator, a second actuator port fluidly coupled with the second chamber of the hydraulically driven actuator, and a pilot operated flow control spool arranged in a spool bore,   a first fail-safe solenoid-controlled pilot valve operably connected to the first directional control valve and configured for driving the flow control spool in a first direction,   a second fail-safe solenoid-controlled pilot valve operably connected to the first directional control valve and configured for driving the flow control spool in a second direction,   a third fail-safe solenoid-controlled pilot valve operably connected to the second directional control valve and configured for driving the flow control spool in the first direction,   a fourth fail-safe solenoid-controlled pilot valve operably connected to the second directional control valve and configured for driving the flow control spool in the second direction, and   redundant pilot pressure fluid supply system having a first pilot pressure fluid supply line and a second pilot pressure fluid supply line configured for supplying pilot pressure fluid to the first to fourth fail-safe solenoid-controlled pilot valves,   wherein each of the first to fourth fail-safe solenoid-controlled pilot valves has a drain passage that is configured to automatically open for enabling automatic drainage of pilot pressure fluid supplied from the pilot pressure fluid supply system in the event a pilot spool of the associated fail-safe solenoid-controlled pilot valve is stuck in an actuated state.   
     
     
         2 . The redundant hydraulic system according to  claim 1 , wherein the hydraulic system further comprises an electronic control system configured for operating the first and third pilot valves in parallel, and for operating the second and fourth pilot valves in parallel. 
     
     
         3 . The redundant hydraulic system according to  claim 1 , wherein the hydraulic system comprises an electronic control system that is configured for operating the first and second pilot-operated directional control valves in parallel. 
     
     
         4 . The redundant hydraulic system according to  claim 2 , wherein the electronic control system is configured for simultaneously supplying same control signals to both the first and third pilot valves, and for simultaneously supplying same control to both the second and fourth pilot valves. 
     
     
         5 . The redundant hydraulic system according to  claim 1 ,
 wherein an inlet port of each of the first and second fail-safe solenoid-controlled pilot valves is connected to the first pilot pressure fluid supply line, and an inlet port of each of the third and fourth fail-safe solenoid-controlled pilot valves is connected to the second pilot pressure fluid supply line, or   wherein the first pilot pressure fluid supply line is connected to a first input port of a shuttle valve and the second pilot pressure fluid supply line is connected to a second input port of the shuttle valve, and an inlet port of each of the first to fourth fail-safe solenoid-controlled pilot valves is connected to an outlet port of the shuttle valve.   
     
     
         6 . The redundant hydraulic system according to  claim 5 , wherein the redundant pilot pressure fluid supply system comprises a first pressure reducing valve configured for supplying pilot pressure fluid to the first pilot pressure fluid supply line, and a second pressure reducing valve configured for supplying pilot pressure fluid to the second pilot pressure fluid supply line. 
     
     
         7 . The redundant hydraulic system according to  claim 6 , wherein an inlet port of each of the first and second pressure reducing valves is fluidly connected for receiving high-pressure hydraulic fluid from the hydraulic fluid pressure source, or for receiving pilot pressure fluid from a dedicated pilot pressure pump. 
     
     
         8 . The redundant hydraulic system according to  claim 1 , wherein the hydraulic system is free from a valve and/or electronic control system configured for actively selectively setting one of the first and second pilot-operated directional control valves in an active state and/or setting the other of the first and second pilot-operated directional control valves in a non-active state in response to a detected malfunction of a part of the hydraulic system. 
     
     
         9 . The redundant hydraulic system according to  claim 1 , wherein a connection point connecting the first actuator port of the first pilot-operated directional control valve with the first actuator port of the second pilot-operated directional control valve is located within the valve assembly, in particular within an input section or end section, or outside of the valve assembly. 
     
     
         10 . The redundant hydraulic system according to  claim 1 , wherein the first and second pilot-operated directional control valves have the same design and functionality. 
     
     
         11 . The redundant hydraulic system according to  claim 1 , wherein the valve assembly is a redundant sectional valve assembly, wherein the first pilot-operated directional control valve is assembled in a first individual work section, wherein the second pilot-operated directional control valve is assembled in a second individual work section, wherein each of the first and second work sections include said inlet port fluidly connected for receiving high-pressure hydraulic fluid from the hydraulic fluid pressure source, said outlet port fluidly connected for draining hydraulic fluid to the hydraulic fluid reservoir, said first actuator port fluidly coupled with the first chamber of the hydraulically driven actuator, said second actuator port fluidly coupled with the second chamber of the hydraulically driven actuator, and said pilot operated flow control spool arranged in a spool bore, and wherein said first and second individual work sections are stacked and clamped together to provide the assembled sectional valve assembly. 
     
     
         12 . The redundant hydraulic system according to  claim 11 , wherein the sectional valve assembly further comprises a inlet section and an end section, wherein the inlet section, the first individual work section, the second individual work section and the end section are stacked and clamped together to provide the assembled sectional valve assembly, and wherein the inlet section and/or end section includes an inlet port and an outlet port. 
     
     
         13 . The redundant hydraulic system according to  claim 12 , wherein the first and second pressure reducing valves and the shuttle valve is located in the inlet section. 
     
     
         14 . The redundant hydraulic system according to  claim 1 , wherein the valve assembly is redundant monoblock valve assembly having a one-piece block with integrally formed inlet port and an outlet port, and with the first and second pilot-operated directional control valves formed either integrally in the block or clamped to a surface of the block. 
     
     
         15 . A vehicle comprising wheels and/or crawlers for facilitating movement of the vehicle and a solenoid-controlled control system comprising a redundant hydraulic system according to  claim 1 , wherein the at least one hydraulic actuator is configured to be used for steering the vehicle. 
     
     
         16 . A method for operating an hydraulically driven actuator of a redundant hydraulic system, the method comprises:
 providing a hydraulic system that comprises a hydraulic actuator; a first pilot-operated directional control valve connected to the hydraulic actuator and a second pilot-operated directional control valve also connected to the hydraulic actuator; first and second fail-safe solenoid-controlled pilot valves operatively connected to the first pilot-operated directional control valve, and third and fourth fail-safe solenoid-controlled pilot valves operatively connected to the second pilot-operated directional control valve;   energizing a solenoid of the first fail-safe solenoid-controlled pilot valve for displacing an associated pilot spool forwards, such that a flow passage opens that supplies pilot pressure fluid from a redundant pilot pressure fluid supply system to a first longitudinal end of a flow control spool of the first directional control valve, and such that high-pressure hydraulic fluid from an external hydraulic fluid pressure source is routed to a first chamber of the hydraulically driven actuator via the first directional control valve, and substantially simultaneously energizing a solenoid of the third fail-safe solenoid-controlled pilot valve for displacing an associated pilot spool forwards, such that a flow passage opens that supplies pilot pressure fluid from the redundant pilot pressure fluid supply system to a first longitudinal end of a flow control spool of the second directional control valve, and such that high-pressure hydraulic fluid from the external hydraulic fluid pressure source is routed to said first chamber of the hydraulically driven actuator via the second directional control valve; and   stopping energizing the solenoid of the first fail-safe solenoid-controlled pilot valve, and substantially simultaneously stopping energizing the solenoid of the third fail-safe solenoid-controlled pilot valve, wherein subsequent rearwards motion of a plunger of the solenoid of the first fail-safe solenoid-controlled pilot valve causes opening of a drain passage in the first fail-safe solenoid-controlled pilot valve for enabling automatic drainage of pilot pressure fluid supplied from the pilot pressure fluid supply system in the event the associated pilot spool is stuck in an actuated state, and wherein subsequent rearwards motion of a plunger of the solenoid of the third fail-safe solenoid-controlled pilot valve causes opening of a drain passage in the third fail-safe solenoid-controlled pilot valve in the event the associated pilot spool is stuck in an actuated state.   
     
     
         17 . A hydraulic system for activating a hydraulic consumer having a first consumer port and a second consumer port, the system comprising:
 a valve assembly having a pressure source inlet port, a reservoir port, a first pilot-operated directional control valve and a second pilot-operated directional control valve, each pilot-operated directional control valve including: a first port fluidly connected to the pressure source inlet port, a second port fluidly connected to the reservoir port, a third port fluidly connected to the first consumer port, a second port fluidly connected to the second consumer port, and a pilot operated flow control spool arranged in a spool bore,   a first fail-safe solenoid-controlled pilot valve operably connected to the first directional control valve and configured for driving the flow control spool in a first direction,   a second fail-safe solenoid-controlled pilot valve operably connected to the first directional control valve and configured for driving the flow control spool in a second direction,   a third fail-safe solenoid-controlled pilot valve operably connected to the second directional control valve and configured for driving the flow control spool in the first direction,   a fourth fail-safe solenoid-controlled pilot valve operably connected to the second directional control valve and configured for driving the flow control spool in the second direction, and   a pilot pressure fluid supply system having a first pilot pressure fluid supply line and a second pilot pressure fluid supply line configured for supplying pilot pressure fluid to the first to fourth fail-safe solenoid-controlled pilot valves,   wherein each of the fail-safe solenoid-controlled pilot valves has a drain passage that is configured to automatically open for enabling automatic drainage of pilot pressure fluid supplied from the pilot pressure fluid supply system in the event a pilot spool of the associated fail-safe solenoid-controlled pilot valve is stuck in an actuated state.   
     
     
         18 . The system of  claim 17 , wherein the valve assembly is a sectional valve assembly. 
     
     
         19 . The system of  claim 17 , wherein the valve assembly is a monoblock valve assembly.